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        <td class="header">&nbsp; Coherence estimation (InSAR operator)</td>
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<h3>Coherence estimation</h3>

<p>
    This operator computes/estimates the coherence image, with or without subtraction
    of the reference phase. The reference phase is subtracted if there is a 2d-polynomial
    computed -- result of "Compute Interferogram" operator. While, it is not subtracted
    if this information is not in the metadata, or if the number of polynomial coefficients
    in "Compute Interferogram" operator is set to 0.
</p>

<p>
    Note that this is a "general" coherence estimation operator and not exclusive only for InSAR
    applications. It can be utilized to estimate the coherence information from
    any stack of coregistered complex images.
</p>

<p>
    In order to reduce the noise, as the post-processing step, you can perform multilooking (with Multilook
    Operator). In case of ESA's ERS and Envisat sensors, the factor 5:1 (azimuth:range) or similar ratio
    between the factors is chosen to obtain approximately square pixels (20x20 m^2 for factors 5 and 1).
    Of course the resolution decreases if multilooking is applied.
</p>

<h4>Operator parameters:</h4>&nbsp;&nbsp;
<p>
    The input parameters are size of the shifting window for the coherence estimation. The window size is
    defined, in both azimuth and range directions.
</p>

<h4>Source bands:</h4>&nbsp;&nbsp;
<p> Source Bands are set of, usually coregistered, bands of the complex product.</p>

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